The present disclosure relates to starter systems and magnetic relay switches used therein, and particularly to controllers for such switches and thus for such systems.
An exemplary starter system of a type used extensively for many years in automotive applications is depicted in FIG. 1. Starter systems for some light-duty passenger car applications have evolved over recent years to the extent that, in some cases, such conventional starter systems, which are solely operator-activated, have been replaced by starter systems having stop-start and/or change-of-mind capabilities that operatively engage a temporarily stopped engine for restarting automatically through use of a controller on the basis of vehicle and engine conditions and sensed operator inputs, without the operator separately initiating starter operation. Nevertheless, conventional starter systems are still commonly utilized today for some light duty applications and many heavy duty applications such as heavy trucks, buses and tractors. It is to be understood, therefore, that herein “conventional” means a starter system in which starter system operation is initiated by the operator, rather than merely to a prior starter system.
Prior conventional starter system 20 shown in FIG. 1 includes starter assembly 22, an operator-actuated starter switch 24, battery 26, and engine ring gear 28 affixed to a flywheel and engine crankshaft 30. Crankshaft 30 and ring gear 28 are rotatable about crankshaft axis of rotation 32. Battery 26 may be a singular battery as shown, or battery 26 may be a plurality of batteries connected in series. Light duty applications typically employ a single 12V battery 26. A pair of series-connected 12V batteries forms a 24V battery 26 commonly used in heavy duty applications including large trucks, buses and tractors. The components of starter system 20 are appropriately sized for the voltage output of its battery 26. Starter systems 20 are typically negatively grounded, as shown, wherein negative terminal 84 of battery 26 is at all times connected to ground 90.
Starter assembly 22 has motor housing/frame structure 34 typically made of electrically conductive material such as steel and houses starter motor 36. Starter motor 36 includes stator windings or coil 38 which, when energized, driveably rotates the rotor (not shown) and output shaft 40 of motor 36. Motor 36 may be connected to ground 90 through motor housing/frame structure 34, which is affixed to and in electrical contact with the grounded engine. Alternatively, motor 36 may be separately grounded. Output shaft 40 is coupled to collar 42 and, in some embodiments, an overrunning clutch 44 as shown. Collar 42 and overrunning clutch 44, if present, are operably coupled to pinion 46 which is rotatable about axis of rotation 48 common to pinion 46 and motor output shaft 40. The provision of overrunning clutch 44 permits pinion 46 to be rotated about axis 48 at an angular speed exceeding that of motor output shaft 40, thereby preventing starter motor 36 from being driven by pinion 46 if the pinion is still engaged with ring gear 28 once the engine starts.
Starter assembly 22 also includes solenoid assembly 50. Solenoid assembly 50 includes axially moveable solenoid plunger 52 and compression spring 53 which exerts a biasing force on plunger 52 that urges it leftwardly as viewed in FIG. 1 into the plunger extended position. Solenoid plunger 52 has end 54 linked to first end 56 of shift lever 58. The opposite second end 60 of shift lever 58 is linked to collar 42. Shift lever 58 is pivotally attached to starter assembly frame structure 34 at a location between shift lever first and second ends 56, 60. As discussed further below, energization of solenoid assembly 50 causes rightward movement of solenoid plunger 52 towards the plunger retracted position that effects pivoting motion of shift lever 58 about its pivot point, whereby pinion 46 is moved leftwardly from its disengaged position towards its engaged position. Pinion 46 is in meshed engagement with ring gear 28, and engine cranking with starter assembly 22 can occur, only in the pinion's engaged position.
Starter system 20 also includes integral magnetic starter relay switch assembly (or IMS) 62 that includes an electromagnetically-actuated relay switch and may be an attached component of starter assembly 22. As shown, IMS 62 has metallic switch housing 64 affixed to and grounded through starter assembly motor housing 34. IMS 62 has switch cover 66 attached to switch housing 64 with a plurality of screws 67. In the embodiment shown, switch cover 66 is provided with relay switch activation terminal 68. IMS 62 has relay switch grounding terminal 70 affixed in electrical communication with the interior of metallic switch housing 64, which is grounded through its attachment to motor housing 34. Those having ordinary skill in the relevant art will recognize, however, that grounding terminal 70 may be insulated from switch housing 64 and separately grounded.
Disposed within switch housing 64 is electromagnetic relay switch activation coil 72 disposed about axially moveable ferrous plunger 74. Activation coil 72 extends between activation terminal 68 and grounding terminal 70. With terminal 70 electrically connected to ground 90, energization of activation terminal 68 induces current flow through activation coil 72, which effects axial movement of plunger 74 against the biasing force of compression spring 75. Electrically conductive contact plate 76 is carried by and electrically insulated from plunger 74. First switch contact 78 is electrically connected to first switch terminal 79 mounted in switch cover 66. Second switch contact 80 is electrically connected to second switch terminal 81 mounted in switch cover 66. First switch contact 78, second switch contact 80 and contact plate 76 define relay switch 83 disposed within IMS 62.
Due to the biasing influence of compression spring 75, contact plate 76 is normally out of contact with first switch contact 78 and/or second switch contact 80, whereby relay switch 83 is biased into an open condition in which first and second switch terminals 79, 81 are out of electrical communication with each other. Current flow through relay switch activation coil 72 electromagnetically moves plunger 74 against the biasing force of spring 75 and brings contact plate 76 into electrical contact with first switch contact 78 and second switch contact 80, whereby relay switch 83 is electromagnetically closed. When closed, relay switch 62 places first and second switch terminals 79, 81 in electrical communication with each other. Positive terminal 82 of battery 26 is in continuous electrical communication with first switch terminal 79, whereby battery voltage is at all times applied to first switch contact 78. Thus, with relay switch 83 closed, battery voltage is provided to second switch terminal 81 of IMS 62.
Operator-actuable starter switch 24 is biased open and its closure by an operator applies voltage to activation coil 72 and commences a starting operation. Starter switch 24 can be of a typical “push-to-make” momentary type such as a key switch commonly used with an ignition key for starting a vehicle engine. Starter switch 24 need not employ a separable key, and may be actuable by an operator through various suitable means known to one having ordinary skill in the art. Starter switch 24 has first and second starter switch contacts 86, 88. First starter switch contact 86 is electrically connected to positive terminal 82 of battery 26. Second starter switch contact 88 is electrically connected to activation terminal 68 of starter relay switch 62. Starter switch 24 is selectively actuated through manipulation by an operator, when moved from its biased open condition and temporarily held by the operator in a closed condition wherein first starter switch contact 86 is in electrical communication with second starter switch contact 88. Thus, with starter switch 24 held closed, battery voltage is applied to relay switch activation terminal 68 and, with terminal 70 electrically connected to ground 90, current is conducted through relay switch activation coil 72, consequently electromagnetically closing relay switch 83 and providing battery voltage to second switch terminal 81 of IMS 62.
Solenoid assembly 50 includes pull-in coil 92 and hold-in coil 94 both disposed about the longitudinal axis of ferrous solenoid plunger 52 and connected to IMS second switch terminal 81. Pull-in coil 92 is connected to motor coil 38, which is connected to ground 90; hold-in coil 94 is directly connected to ground 90. Current flow received by starter motor coil 38 from pull-in coil 92 is insufficient to operably drive motor 36. Indeed, in conventional starter system such as starter system 20, it is generally undesirable to rotate the pinion 46 prior to its engagement with engine ring gear 28. Solenoid assembly 50 includes first and second solenoid switch contacts 96, 98 which are selectively electrically connected through solenoid contact plate 100 insulated from and carried by solenoid plunger 52. First and second solenoid switch contacts 96, 98 and solenoid contact plate 100 define solenoid switch 102, which is biased open under the influence of compression spring 53 acting on solenoid plunger 52.
First solenoid switch contact 96 is electrically connected to battery positive terminal 82, whereby it is continuously provided with battery voltage. As shown, first switch terminal 79 is connected to first solenoid switch contact 96, through which battery voltage is provided to first switch terminal 79. Second solenoid switch contact 98 is located between pull-in coil 92 and motor coil 38. The closing of starter relay switch 62 and consequent application of battery voltage to second switch terminal 81 directs current through pull-in coil 92 and hold-in coil 94, which urges solenoid plunger 52 rightwardly, as viewed in FIG. 1, against the biasing force of compression spring 53, to establish and maintain electrical communication between first and second solenoid switch contacts 96, 98 through contact plate 100 carried by solenoid plunger 52, thereby placing solenoid switch 102 in its closed state. The rightward movement of solenoid plunger 52 also urges pinion 46 leftwardly toward engagement with ring gear 28.
With solenoid switch 102 closed, motor-energizing battery voltage is applied to starter motor coil 38, thereby starting operable rotation of motor 36 and pinion 46. With solenoid switch 102 closed, battery voltage is also applied to both ends of pull-in coil 92, thereby halting current flow therethrough and causing a reduction in the total electromagnetic force on solenoid plunger 52 that opposes compression spring 53. The rightward position of solenoid plunger 52 is then maintained by the electromagnetic force generated by current flow through hold-in coil 94, to which battery voltage remains applied via second switch terminal 81. The interruption of current flow through solenoid hold-in coil 94, as would result from the opening of starter switch 24 and, consequently, relay switch 83, allows compression spring 53 to move solenoid plunger 52 and contact plate 100 leftwardly, which urges pinion 46 out of engagement with ring gear 28 through shift lever 58, and interrupts electrical communication between first and second solenoid switch contacts 96, 98, thereby de-energizing motor 36.
It is well-known by those having ordinary skill in the art that prior conventional starter systems have been susceptible to one or more of several well-known problems or failure modes:
A first such problem or failure mode includes incidences of “click-no-crank” occurrences wherein the axial face of the starter assembly pinion is driven into abutment with the interfacing axial surface of the engine ring gear 28, rather than their respective teeth becoming enmeshed. Such incidences involve energization of the starter solenoid assembly 50 during operator activation of switch 24, which results in the pinion-ring gear abutment (typically resulting in an audible “click”) blocking movement of solenoid switch contact plate 100 into electrical contact with first solenoid switch contact 96 and second solenoid switch contact 98, thereby preventing solenoid switch 102 from closing. Prolonged application of electrical power to solenoid assembly 50 during an abutting condition between the faces of pinion 46 and ring gear 28 can prevent meshed engagement therebetween. The necessary meshing between these gears cannot be accomplished if the abutting faces remain in contact under force.
In some prior conventional starter system embodiments, such as system 20 shown in FIG. 1, solenoid switch 102 being prevented from closing causes electrical power to be applied to solenoid assembly 50 through relay switch 83 while starter switch 24 is closed. An operator holding starter switch 24 closed while solenoid switch 102 remains open causes current to flow from battery 26 to ground 90 through relay switch 83 and solenoid coils 92 and/or 94, and can quickly drain battery 26. Moreover, the energization of motor 36 provided via solenoid pull-in coil 92 while solenoid switch 102 is prevented from closing is often insufficient to rotate pinion 46 into a position wherein it can be received into its engaged position, wherein it is enmeshed with ring gear 28 and closure of solenoid switch 102 occurs. Thus, in the case of some prior starter systems, while the audible noise and need for the operator to open and reclose starter switch 24 to commence a new starting operation can be annoying, “click-no-crank” occurrences can lead to further starting attempts being unsuccessful due to a consequent lack of available cranking power.
One prior approach to solving the problems of “click-no-crank” occurrences or the consequences of solenoid prolonged power application that is well-known to those having ordinary skill in the art has involved configuring a starter assembly with a “soft start” starter motor engagement system whereby the pinion and the ring gear are enmeshed before full electrical power is applied to the starter motor. Another such approach has been configuring the starter assembly include a jump spring acting between the solenoid plunger and the pinion, which allows the plunger to continue its axial movement and accomplish solenoid switch closure and motor energization despite abutting engagement occurring between axially interfacing pinion and ring gear faces, the jump spring urging the pinion axially into meshed engagement with the ring gear as the pinion begins to rotate. Nevertheless, for reasons of cost, reliability and/or complexity, or for other reasons, the above-mentioned prior approaches have not been incorporated into some starter systems, particularly those for heavy duty applications.
A second such problem sometimes encountered with prior conventional starter systems such as starter system 20, is that starter motor energization may occur prior to pinion 46 being positioned to mesh with the ring gear 28, which can result in damage to the pinion and ring gear teeth. Even if starter motor 36 is no longer energized, rotating inertia of its rotor, output shaft 40 and pinion 46 may cause it to continue rotating during rapid re-engagement of pinion 46 with ring gear 28. Such occurrence may happen when the operator does not fully depress the vehicle clutch pedal during engine starting, which typically results in a lockout of starter system operation. Those having ordinary skill in the art often refer to these problematic re-engagements as being caused by an operator's “lazy clutch foot.” Pinion 46, when unloaded typically rotatable at between 3500 and 6500 RPM, may thus intermittently contact ring gear 28 due to inadvertent repeated engagement of starter assembly 22, which can result in damage to the pinion and ring gear teeth.
A third such problem sometimes encountered with prior conventional starter systems such as starter system 20 relates to engagement of the starter assembly 22 with an already running engine. Engagement of pinion 46 with the already spinning ring gear 28 can also result in damage to the pinion and ring gear teeth.
A fourth such problem sometimes encountered with prior conventional starter systems such as starter system 20 relates to solenoid chatter resulting from low battery voltage. In such cases the low battery voltage level is sufficient to energize the solenoid assembly 50 and move the plunger 52 and the pinion 46 axially (and in some embodiments to close solenoid switch 102), but it is insufficient to allow starter motor 36 to rotate the pinion, much less crank the engine. In such cases solenoid assembly 50 may not cause pinion 46 to fully enter into meshed engagement with the ring gear 28. Solenoid chatter can result from repeated impact between axially interfacing surfaces of the pinion 46 and engine flywheel 28, or from oscillating, axially opposite movements of the solenoid plunger 52 which are induced by the pull-in coil 92 and the biasing compression spring 53, near the position into which it is biased by the compression spring 53.
A fifth such problem sometimes encountered with prior conventional starter systems such as starter system 20 relates to overcranking conditions in which starter assembly 22 is allowed to crank continually, which may occur if the engine does not start as desired. Overcranking can result in higher than desired temperatures in the starter assembly 22, and thermal degradation of its components over time. Moreover, overcranking can lead to battery 26 being drained to such an extent that insufficient cranking power is delivered to the motor 36.
A sixth such problem sometimes encountered with prior conventional starter systems such as starter system 20 which lack an overrunning clutch 44, is the overrunning of starter motor 36 by the started engine. This can occur, for example, if pinion 46 fails to disengage ring gear 28 upon the engine's starting. Overrunning of starter motor 36 can result in undesirably high starter temperatures and thermal degradation, and in some starter system embodiments can cause starter motor 36 to undesirably operate as a generator. As noted above, overrunning clutch 44, if present, allows pinion 46 to be driven by ring gear 28 beyond the rotational speed of motor output shaft 40. Nevertheless, extended overrunning of pinion 46 decoupled from motor output shaft 40 can result in overrunning clutch 44 experiencing undesirably high temperatures and thermal degradation.
It is desirable to address these well-known problems occurring in conventional starter systems. Moreover, it is particularly desirable to provide a conventional starter system that avoids these problems or failure modes and operates independently of other vehicle systems, and controls starter operation without being receivable of a signal indicative of a measured engine speed, whether from outside the starter system, as from another system or an ECU, or from a dedicated engine speed sensor.
Notably, certain starter system applications, particularly heavy duty vehicle or engine applications, may be of a type which either do not already utilize a measured engine speed signal, or which require significant cost and additional complexity to make a currently existing engine speed signal available for use in regulating a starter system. A stand-alone, controllable starter system that avoids the above-mentioned problems and is operable independently of other vehicle systems and without requiring a signal indicative of a measured engine speed, would be particularly desirable for use in certain applications.